<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    * {
      padding: 0;
      margin: 0;
    }
  </style>
</head>

<body>
  <canvas id="canvas"></canvas>
  <!-- 顶点着色器 -->
  <script id="vertexShader" type="x-shader/x-vertex">
    void main() {
        gl_Position = vec4(0.0, 0.0, 0.0, 1.0);
        gl_PointSize = 100.0;
    }
</script>
  <!-- 片元着色器 -->
  <script id="fragmentShader" type="x-shader/x-fragment">
    void main() {
        gl_FragColor = vec4(1.0, 1.0, 0.0, 1.0);
    }
</script>
  <script>
    // canvas 画布
    const canvas = document.getElementById('canvas');
    canvas.width = window.innerWidth;
    canvas.height = window.innerHeight;
    // webgl画笔
    const gl = canvas.getContext('webgl');
    // 顶点着色器
    const vsSource = document.getElementById('vertexShader').innerText;
    // 片元着色器
    const fsSource = document.getElementById('fragmentShader').innerText;
    // 初始化着色器
    initShaders(gl, vsSource, fsSource);
    // 指定将要用来清理绘图区的颜色
    gl.clearColor(0., 0.0, 0.0, 1.0);
    // 清理绘图区
    gl.clear(gl.COLOR_BUFFER_BIT);
    // 绘制顶点
    gl.drawArrays(gl.POINTS, 0, 1);

    function initShaders(gl, vsSource, fsSource) {
      //创建程序对象
      const program = gl.createProgram();
      //建立着色对象
      const vertexShader = loadShader(gl, gl.VERTEX_SHADER, vsSource);
      const fragmentShader = loadShader(gl, gl.FRAGMENT_SHADER, fsSource);
      //把顶点着色对象装进程序对象中
      gl.attachShader(program, vertexShader);
      //把片元着色对象装进程序对象中
      gl.attachShader(program, fragmentShader);
      //连接webgl上下文对象和程序对象
      gl.linkProgram(program);
      //启动程序对象
      gl.useProgram(program);
      //将程序对象挂到上下文对象上
      gl.program = program;
      return true;
    }

    function loadShader(gl, type, source) {
      //根据着色类型，建立着色器对象
      const shader = gl.createShader(type);
      //将着色器源文件传入着色器对象中
      gl.shaderSource(shader, source);
      //编译着色器对象
      gl.compileShader(shader);
      //返回着色器对象
      return shader;
    }
  </script>
</body>


</html>